Remembering a Qadhaa salaah after Joining the Jamaa'ah

Q: Salaah-491: A person remembered that he had not performed the previous salaah only after joining the Jamaa'ah for the salaah. What is he to do?

Answer: If the person is Saahibut Tarteeb, he should complete the salaah with the Imaam, perform the previous salaah he missed and then repeat the salaah he performed behind the Imaam. This will however not be necessary if he is not SaahibutTarteeb. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2